1. Field of the Invention
The present invention relates generally to daylight cameras, and more particularly to vacuum feed assemblies which automatically transport photosensitive materials through the sequence of operations of such cameras.
2. Description of the Prior Art
The commercial appeal of a daylight camera that could automatically remove film from a storage receptacle, cut same to length, expose same, and transport the exposed film to a developer station has long been recognized. However, such objective has not yet been realized, although progress has been made in this quest by numerous conventional graphic arts systems. As an example, U.S. Pat. No. 4,089,603 granted May 16, 1978 to Robert D. Jacobs, and now assigned to Itek Graphix Corp. of Waltham, Mass., discloses a high speed vacuum support assembly for platemakers. The apparatus includes a first cover plate assembly having a transparent cover plate, and a second backing plate assembly including a relatively flexible backing sheet. The cover plate assembly is driven, by a motor, into contact with the photosensitive sheet supported therebetween, so that an airtight chamber is defined therebetween. The airtight chamber is evacuated (by a vacuum source) so that the flexible backing plate will be sucked toward the cover plate assembly, and drive the photosensitive sheet into film contact with the transparent cover plate.
U.S. Pat. No. 4,408,872, granted Oct. 11, 1983 to Quentin D. Vaughan, and assigned to Visual Graphics Corporation of Tamarac, Fla. discloses a vertically oriented, daylight camera system of particular relevance. This patent discloses a system in which a camera supports a table along which a cassette carriage is manually propelled. The carriage serves to store, and feed out, lengths of photosensitive material into a camera exposure station.
A source of vacuum acting between a sheet of flexible, opaque plastic material and a translucent glass platen for the camera at the exposure station causes the film to be flattened against the platen prior to film exposure. Thereafter, vacuum is broken by movement of the carriage, and the exposed film is urged into the nip of rollers which carry the film through a developing station supported by the table. The exposed film is advanced toward the developing station by a brush-like member which picks up the trailing edge of the film; the brush-like member is secured beneath carriage 26.
U.S. Pat. No. 4,479,710, granted Oct. 30, 1984 to Quentin D. Vaughan, discloses refinements in the daylight camera system disclosed in U.S. Pat. No. 4,408,872, also granted to Quentin D. Vaughan and assigned to Visual Graphics Corporation of Tamarac, Fla. For example, U.S. Pat. No. 4,479,710 discloses protuberances formed on the underside of the flexible, opaque plastic sheet that is advanced by the manually operated cassette carriage across the platen of the camera; the protuberances insure smooth passage of the photosensitive material as it slides across the platen beneath the plastic sheet. U.S. Pat. No. 4,479,710 also discloses an elongated vacuum bar that assists in removing air from beneath the plastic sheet, as well as to be more easily lifted from the platen after the vacuum draw-down is terminated.
While the two patents granted to Quentin D. Vaughan represent improvements over previously known graphic arts systems, the Vaughan cameras rely upon manual operation of a cassette carriage in order to advance a length of photosensitive material, cut same to length, and advance the exposed film to a processing station. The back and forth movement of the cassette carriage across the table of the camera requires the continued presence of an operator, and increases the cost of operating the camera. The need to move the carriage in finite steps, to distinct locations on the table of the camera, calls for careful operation of the camera system, and reduces, potentially, the operational speed of the system. Also, to maintain the light-tight characteristic of the daylight camera system, Vaughan relies upon an elongated, flexible opaque sheet of plastic that is unwound from a roller situated at the rear of the cassette carriage; the effectiveness of this seal may diminish after extended use and stray light may enter the camera system.